1. Field of the Invention
This invention relates to a method for correcting the optical system of an eye using an intraocular lens system. Particularly, this invention relates to a method of correcting focusing abnormalities and optical aberrations measured by wave front or similar technology to quantify optical aberrations in the optical system of the eye, using a laser, or other apparatus and/or methods of fabricating or modifying a lens, for the optical system of an eye having a foldable, interchangeable intraocular lens system provided therein.
2. Description of Related Art
The field of refractive surgery has evolved rapidly during the past few decades. Current procedures and methods used by refractive surgeons may not satisfy the total refractive needs of the patient. Particularly, the most commonly performed refractive surgical procedures, such as, for example, cataract extraction with intraocular lens implantation, in addition to the most recently popularized corneal refractive surgical procedures, such as eximer laser photoblation, exhibit limitations. One reason for the limitations is the lack of post-operative refractive accuracy. The lack of post-operative refractive accuracy renders the commonly known refractive surgical procedures uncompetitive with currently available non-surgical alternatives for patients, for example, glasses and contact lenses. Further, because refractive surgery requires local or general anesthesia and incisions into the eye, a need exists for decreasing the trauma resultant from the surgery.
Recently, a need has arisen for efficient treatment of presbyopia, or the diminished power of accommodation of the eye. Presbyopia is a condition which typically affects a large number of people as they age, with the severity of the condition varying depending on the person. Difficulties arise in treating presbyopia because typically once a person manifests symptoms of presbyopia, the symptoms worsen as the person ages. As a person's condition worsens, a different, usually more powerful, lens is required to correct the condition. Conventional techniques for replacing an intraocular lens each time the patient's vision deteriorated do not always present a practical or cost-effective approach. Recent developments in the field, of refractive surgery have made intraocular treatment of presbyopia a feasible course of treatment for those patients that desire or need improved vision, however a need exists for more precise techniques and devices for use in refractive intraocular surgery.
Patients suffering from eye trauma or other eye afflictions may have the iris or other portions of the eye distorted, destroyed, or discolored. Currently, such patients are typically prescribed cosmetic contact lenses. Cosmetic intraocular lens replacement is emerging as a viable alternative, however a need exists for more efficient intraocular lens replacement in order to minimize eye trauma and establish cosmetic intraocular lens replacement as a safe and effective alternative to cosmetic contact lenses and other non-surgical treatments. As surgical techniques become more effective, safer, and less painful, patients may choose to have elective lens replacement surgery to change the color, structure, or shape of their eyes. By providing a minimally invasive method for lens replacement as described in an embodiment herein, the surgeon is able to limit the drawbacks of the procedure.
Current procedures and methods for refractive surgery require the performing surgeon to execute the procedure with a high level of skill and experience. Currently, methods and procedures for carrying out refractive surgery involving intraocular lenses generally require direct visualization of the intraocular lens assembly within the eye. Such visualization, although not outside the scope of a surgeon skilled in the art, increases the degree of difficulty of the procedure, thus increasing the chance that a surgical error or other problem will arise in the surgical procedure, leading to unwanted complications. Thus, a need exists for intraocular lens assemblies and systems whose structures provide less complex methods of insertion into and extraction from the eye.
Currently, refractive cataract surgeons performing the most common refractive surgical procedure, i.e., routine cataract surgery, obtain refractive accuracies in a +/−0.75 to +/−1.00 diopter (D) range. However, the industry has established goals of obtaining refractive accuracies in the +/−0.25 D range. Therefore, there is a need in the industry to provide a more accurate alternative to the current procedure. Furthermore, analyses of current corneal refractive technologies indicate the presence of a significant amount of preexisting or naturally occurring post-operative, as well as preoperative, image distortion (optical aberration) or degradation, particularly under low light conditions, such as when driving at night.
Due to the practical limits of performing intraocular surgery, as well as the biological and physical behavior of the human eye during and after various types of intraocular surgery, predictability at the +/−0.25 D accuracy level with a single surgical procedure is difficult to achieve as a practical matter. Furthermore, factors such as biometry errors, variable wound healing, and capsular contraction around the intraocular lenses contribute to decreasing the likelihood of achieving the desired refractive accuracy. Accordingly, practitioners in the industry have found that an adjustable intraocular lens (IOL), hereinafter referred to as the MC-IOL (multi-component) or C-IOL (compound), following lens extraction surgery provides a plurality of desirable options for refractive surgeons and patients.
An adjustable IOL allows fine tuning of the initial refractive result by exchanging at least one of the optical elements of the lens implant. As a result, accuracies in the +/−0.25 D range are readily attainable. Furthermore, patients are provided with an opportunity to exchange the “old” lens components with new and hopefully more accurate components. Such an objective is obtainable if the surgeon has an effective, efficient, and safe method of performing lens element exchanges. Additionally, months and/or years after the refractive surgical procedure, if the optical properties of the inserted IOL, for example, the multifocality, become problematic, the surgeon should have the ability to safely exchange the undesirable optical elements of the IOL to correct any optical aberrations that the patient will not or cannot tolerate.
In 1990, the inventor of this application developed a multi-component intraocular lens, hereinafter referred to as the MC-IOL (FIG. 1), for use following clear lens or refractive cataract surgery, wherein the optical properties of the MC-IOL can be modified at any post-operative time. The base intraocular lens component of the MC-IOL is shown in FIG. 1. The mid lens attaches to the top of the base lens and holds the third component of the MC-IOL, the top lens, in place.
The base intraocular lens 10 and the mid lens 20 each have securing flanges 16, 18 and 20, 24, respectively, extending therefrom. The MC-IOL also comprises at least one top lens 30, as illustrated in FIG. 1. The top lens 30 is positioned on top of the mid lens 20. See FIGS. 1-2.
The MC-IOL also includes projections (or haptics) 11 and 13 which securely hold the MC-IOL in the tissue of the human eye. The above-described structure permits the base intraocular lens 10 to form a platform upon which the mid lens 20 is placed, and to hold the top lens 30. During routine cataract surgery, the MC-IOL replaces the crystalline lens of the human eye. Once a patient's eye has healed after such a surgery, the surgeon reenters the eye and replaces, if necessary, and more than once, the top lens 30 and the mid lens 20 to modify the optical characteristics of the eye until the desired levels for each optical characteristic are attained.
FIGS. 3A-3B illustrate an assembled compound intraocular lens, hereinafter C-IOL, used with a preexisting lens within the human eye. The C-IOL has two components similar to the mid lens (FIGS. 4A-4B) and the top lens (FIGS. 5A-5B) components of the MC-IOL. FIG. 5A also illustrates the axis orientation mark 85 used in some embodiments of MC-IOL lenses, to aid in positioning and orienting the lens. The preexisting lens can be the crystalline lens of the eye with the C-IOL placed in the sulcus (FIG. 6) or in the anterior chamber angle (FIG. 7) of the eye's optical system. However, the C-IOL can also be used with a conventional IOL, as well as with an accommodating IOL, and mounted in the sulcus (FIG. 8), in the anterior chamber angle (FIG. 9), in the anterior chamber with posterior chamber fixation (FIG. 10) or in the anterior chamber with iris fixation (FIG. 11). Thus, a surgeon modifies the optical characteristics of the optical system of the eye by using the mid and top lenses in tandem with the preexisting conventional IOL implant or crystalline lens of the eye.
The C-IOL and MC-IOL provide numerous enhanced features. For example, the C-IOL and MC-IOL can each be structured as a monofocal or multifocal optical system, correct astigmatism, as well as comprise ultraviolet light-absorbing, tinted, or other such chemically treated materials.
It should be understood that there are various reasons why an adjustable MC-IOL or C-IOL is more desirable than a single component implant. In order to achieve all the permutations and combinations of the astigmatism, multifocality, and spherical correction needed to achieve emmetropia would take an inventory of over ten thousand lenses, whereas with the MC-IOL (multiple components) concept, an inventory of about one hundred components would be necessary. With anterior chamber lenses, progressive encapsulation or engulfment of the lens haptics by uveal tissue in the angle often occurs 1-2 years post-operatively. The engulfment typically makes the removal of the lenses and their haptics more difficult. Exchange of iris fixated anterior chamber lenses does not typically guarantee precise position or orientation. Posterior chamber lenses similarly cannot be removed because of posterior capsule fibrosis. Easy removal and exchangeability is critical for any customized emmetropic system, which can be provided by a specially designed multicomponent lens system.
Therefore, based on the above, a MC-IOL having three elements rather than one permits refractive customization and adjustability for all refractive errors, as well as for all patients, while using a minimal number of lens elements or parts and requiring little customization on the part of the manufacturer. Thus, it has become very important in the refractive surgery art to be able to individualize and/or customize surgery such that the surgeon can easily and safely, as well as accurately, modify the refractive power of an intraocular lens implant.
For example, U.S. Pat. No. 5,288,293 to O'Donnell, Jr. discloses a method of modifying a single IOL. O'Donnell suggests that the refractive power of a single IOL may be varied before implantation so that the changes can be made in situ by the ophthalmologist after determining the extent of correction required to improve the vision of the patient before the lens is made. However, the surgical implantation procedure itself may create additional optical aberrations which cannot be anticipated preoperatively and thus the primary lens implant cannot account for these optical aberrations.
As such, it may be argued that if a lens can be modified before being implanted, as suggested by O'Donnell, Jr., it should be possible to modify the implanted lens by removing the implanted lens, modifying the lens, and then reimplanting the modified lens into the optical system of the eye. However, the design of current intraocular lenses typically makes such a procedure difficult and impractical. Furthermore, after a period of time with normal healing, it becomes physically dangerous and/or nearly impossible to the patient to have the implanted lens removed once the eye tissue takes hold on the capsular fixation holes of the lens. Therefore, such an argument is not realistic, practical, or safe. A single component intraocular lens, which in general is not designed to be removed and with only two optical surfaces, cannot accurately allow for compensation of sphere, cylinder, cylindrical axis, and all forms of optical aberrations that may be discovered after the initial implantation. However, the MC-IOL typically will have four removable optical surfaces which can compensate for these optical properties.
The inventor of this application invented the previously discussed MC-IOL and C-IOL that are designed specifically to permit the easy exchange of optical elements at a post-operative period without risk to the human eye or to the patient, beyond the risk of ordinary intraocular surgery. The easy exchangeability of optical elements is critical because the actual surgery of implanting the lens in the first place, as well as variances in the manner in which the eye heals after implantation, potentially create distortions which may not stabilize for several months after the operation. Therefore, the ability to measure and to compensate for the distortion(s) optimally takes place several months after surgery and cannot typically be predicted prior thereto. Since the same surgical wound is used for both the primary and secondary operations, additional distortion due to wound healing would not be anticipated as a result of the second operation.
Furthermore, the ability to exchange optical elements of a multicomponent or compound intraocular lens can be economical compared to removing, modifying, and re-implanting a single component lens, as well as easier to perform.
The MC-IOL has four surfaces available for modification, two piano and two convex. Preferably, the modification is made only to the piano surfaces to avoid interfering with the convex side which may already be used for correction of astigmatism (cylinder) or used as a multifocal lens surface. The same preference applies to the CIOL, which has two surfaces available for modification, one piano and the other convex.
The inventor of this application also developed a system for correcting optical aberrations in the MC-IOL, as described, for example, in U.S. Pat. No. 6,413,276, for conducting measurements to determine any residual or new aberrations present in an operated eye after the biological healing parameters have stabilized, as well as to correct any errors in sphere, cylinder, or cylindrical axis, and for modifying one, two, or more existing lens elements within the implanted optical system based on the conducted measurements.
In conventional multi-component intraocular lens designs, the surgical procedure required to implant the intraocular lens components requires a high level of surgeon skill. For example, implantation of the removable component of the lens requires the surgeon to directly visualize the placement of the lens in order to match the notches with the flanges. Further, removal of the removable lens component requires a special forceps tool for grabbing the base lens, and releasing the tabs holding the sandwich and cap lens together with the base lens (see, for example, the system described in U.S. Pat. No. 5,968,094).
Historically intraocular lens systems used a rigid one piece poly methyl methacrylate (PMMA) lens. The PMMA lens is approximately six millimeters in diameter. Because the PMMA lens is rigid, insertion of the PMMA intraocular lens generally requires a seven or eight millimeter incision to be inserted into the eye. In contrast, a flexible or foldable lens can be manipulated and compacted to a much smaller size. Once compacted, the multi-component intraocular lens can be delivered using a relatively smaller incision, for example, about three millimeters or less. By using a smaller incision, the patient reaps optical and practical benefits. From an optical standpoint, any time incisions are made to the cornea, the cornea loses some of its natural globularity due to imperfections caused by the incisions and the resultant trauma. The imperfections in the cornea lead to induced astigmatism, or optical aberrations caused by irregularities in the shape of the cornea. By minimizing the size of the corneal incision, a surgeon may also minimize the amount of induced astigmatism. Even though the three-component design simplifies the process of correcting induced astigmatism, minimizing the amount of induced astigmatism remains a primary goal for all intraocular surgeries.
As a practical matter, by making a smaller incision, the surgeon reduces the amount of actual trauma to the eye, thus reducing the occurrence of complications and decreasing the time for recovery. These advantages are further realized if the surgeon is able to perform the intraocular surgery using an incision small enough to heal without the use of stitches, wherein the incision is small enough to allow the eye's natural ocular pressure to hold the incision together during the healing process.
The inventor's application Ser. No. 11/698,875 overcame the above-described drawbacks of the related art. FIGS. 12-16 illustrate the invention disclosed in the '875 patent application.
For example, FIG. 12A shows a top or plan view of an intraocular foldable base lens 100, which is similar to the MC-IOL base lens illustrated in FIG. 3. The base lens 100 attaches to the eye by at least one haptic 120 and while the base lens 100 in FIG. 12A can be secured to the eye by at least one haptic, it is preferable that at least two haptics 120 be used. As shown in FIG. 12A, each haptic 120 extends outward from the base lens 100, and is tilted from between 10 to 20 degrees, in either direction, relative to a plane taken across the base lens, preferably having a 15 degree positive tilt.
As shown in FIG. 12B, the base lens 100 can also include one or more flanges 105 disposed on and extending outwardly away from the body of the base lens 100. Each flange 105 can also have a slot 110 designed or configured to receive or accept an assembly of a top lens 300 and a mid lens 200 therein.
The base lens in FIG. 13 is similar to the base lens 100 (FIGS. 12A-12B), except for a groove 130 being defined therein that extends along the entire outer periphery, and a plurality of attachment points 140, which serve to attach the optical region 150 to the base lens.
The foldable MC-IOL disclosed in the inventor's '875 application includes two or more additional refractive components, i.e., a top lens 300 and a mid lens 200. The mid lens 200, which typically allows spherical adjustments, is illustrated in FIGS. 14A-14B, while the top lens 300 (FIG. 15) carries the astigmatic correction and has an orientation projection 305. The mid lens 200 may include at least one projection 210 extending away from the body of the mid lens 200 and may have varying lengths depending on the shape and number of projections. The mid lens 200 also includes a side portion 250 which extends upward, and terminates at a lip 225, as illustrated in FIG. 14B. The side portion 250 and lip 225 extend along the outer circumference of the mid lens 200, thereby defining a notch 230.
Prior to insertion into the eye, the top lens 300 engages the notch 225 of the mid lens, such that a seal is formed between the notch 225 and the top lens 300, and which holds the mid lens 200 and the top lens 300 together as a single assembly. The top lens 300 is oriented so that, when the top lens 300 is inserted into the mid lens 200, raised projections or notches 305 of the top lens 300 face the mid lens 200 or may also project away from the mid lens 200. The notches or projections 305 can provide directional and axial orientation for the top lens, similar to the axis orientation marks 85 of FIG. 5.
The surgeon performing the operation or the lens manufacturer assembles the mid lens 200 and the top lens 300 outside the eye to a predetermined axis orientation to correct the astigmatism, and then inserts the completed assembly into the eye as one folded piece such that the mid lens 200 is sandwiched between the base lens 100 and top lens 300. The surgeon inserts the top lens 300 and the mid lens 200 assembly into the base lens 100 by sliding a projection 210 of the mid lens 200 into a slot 110 of a corresponding flange 105 of the base lens 100. Once the first projection 210 is in place in the corresponding first slot 110, if more projections are present in the mid lens 200, then the surgeon adjusts the mid lens 200 and the top lens 300 until the other projection(s) 210 line up with the other slot(s) 105. Once all projections 210 have been inserted into their corresponding slots 110, the assembly of the top lens 300 and the mid lens 200 is secured in the base lens 100, and the procedure is completed.
In the event that the assembly formed by the mid lens 200 and the top lens 300 requires replacement, the surgeon may perform a disassembly procedure as discussed herein. First, a cannula containing visco elastic material would be introduced into the eye and positioned at the interface between the lens assembly (mid lens 200 and top lens 300) and the base lens 100. The injection of visco elastic causes the mid 200/top 300 lens assembly to elevate, thus disengaging the projections 210 from the slots 110 in the base lens 100. The original lens assembly would then be removed from the eye, and a new lens assembly placed into the eye and attached to the base lens 100 similar to as described above in the primary operation.